CAD apparatus, method, and computer product for designing printed circuit board

ABSTRACT

In a computer aided design (CAD) apparatus, an association-data acquiring unit acquires association data that defines an association between pins of a first connector and those of a second connector to be connected to the first connector, and an assignment of signals to the pins. A part-information acquiring unit acquires information including a symbol of the first connector. A layout-condition acquiring unit acquires a layout condition to lay out the symbol of the first connector on a circuit diagram. A circuit diagram creating/updating unit lays out the symbol of the first connector on the circuit diagram based on the layout condition, and adds a net name indicating a signal assigned to each of the pins to the symbol.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a computer aided design (CAD)apparatus, a method, and a computer product for designing a printedcircuit board.

2. Description of the Related Art

An electronic circuit that controls an information processing apparatus,a communication device, or the like generally includes a plurality ofprinted circuit boards connected to each other via connectors. Designwork of such an electronic circuit requires to check whether signals arecorrectly assigned to pins of the connectors by comparing pieces ofdesign information of the printed circuit boards.

To easily and reliably perform the checking operation, some conventionaltechnologies have been proposed. For example, Japanese PatentApplication Laid-Open No. H8-69486 discloses a connector-informationcheck apparatus. The connector-information check apparatus readsattribute information of a connector pin and a signal from a circuitdiagram-file of a printed circuit board and that from a circuit diagramfile of another printed circuit board to be connected to the former one,and compares the pieces of the attribute information. Japanese PatentApplication Laid-Open No. 2001-325315 discloses a multi-PCB-connectiondesign support apparatus. The multi-PCB-connection design supportapparatus logically traces a signal line between printed circuit boardsconnected via a back wiring board to verify that a signal is correctlyassigned to a connector pin.

The conventional technologies improve efficiency of the checkingoperation performed after design of printed circuit boards to beconnected via connectors is once completed; however, these technologiesdo not improve efficiency of designing a printed circuit board itself.Recently, a product is developed in a shorter span, and thus, there is aneed of a technology for improving efficiency of designing a printedcircuit board.

SUMMARY OF THE INVENTION

It is an object of the present invention to at least partially solve theproblems in the conventional technology.

According to an aspect of the present invention, computer aided design(CAD) apparatus for designing a circuit diagram, includes anassociation-data acquiring unit that acquires association data thatdefines an association between a pin of a first connector and a pin of asecond connector to be connected to the first connector and anassignment of a signal to the pins, a part-information acquiring unitthat acquires information including a symbol of the first connector, alayout-condition acquiring unit that acquires a layout condition to layout the symbol on the circuit diagram, and a circuit diagram editingunit that lays out, when the symbol has not yet been laid out on thecircuit diagram, the symbol on the circuit diagram based on the layoutcondition, and adds a net name indicating the signal assigned to thepins to the symbol.

According to another aspect of the present invention, a method ofdesigning a circuit diagram includes acquiring association data thatdefines an association between a pin of a first connector and a pin of asecond connector to be connected to the first connector and anassignment of a signal to the pins, acquiring information including asymbol of the first connector, acquiring a layout condition to lay outthe symbol on the circuit diagram, and laying out, when the symbol hasnot yet been laid out on the circuit diagram, the symbol on the circuitdiagram based on the layout condition, and adding a net name indicatingthe signal assigned to the pins to the symbol.

According to still another aspect of the present invention, acomputer-readable recording medium stores therein a computer programthat implements the above method on a computer.

The above and other objects, features, advantages and technical andindustrial significance of this invention will be better understood byreading the following detailed description of presently preferredembodiments of the invention, when considered in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of printed circuit boards to be connected by aconnector;

FIG. 2 is a schematic diagram of a design support system according to anembodiment of the present invention;

FIG. 3 is a functional block diagram of a check support apparatus shownin FIG. 2;

FIG. 4 is an example of a check screen that displays information on aprinted circuit board of level 1;

FIG. 5 is the check screen of FIG. 4 that further displays informationon a printed circuit board of level 2;

FIG. 6 is an example of an association screen that displays two sets ofassociated pins;

FIG. 7 is an example of physical layout of pins;

FIG. 8 is an example of the association screen after pin information issorted;

FIG. 9 is another example of physical layout of pins;

FIGS. 10 and 11 are other examples of the association screen after pininformation is sorted;

FIG. 12 is another example of physical layout of pins;

FIGS. 13 to 16 are other examples of the association screen after pininformation is sorted;

FIG. 17 is an example of the check screen after association is defined;

FIG. 18 is an example of the check screen after association is checked;

FIG. 19 is a flowchart of a processing procedure of association check;

FIG. 20 is an example of contents of an association file;

FIG. 21 is an example of the structure of design data;

FIG. 22 is an example of the structure of association data;

FIG. 23 is a functional block diagram of a CAD apparatus shown in FIG.2;

FIG. 24 is an example of a circuit diagram to be created;

FIG. 25 is an example of a circuit-diagram creation/update screen;

FIG. 26 is an example of layout of parts when the parts are sequentiallyarranged;

FIG. 27 is an example of layout of parts when identical parts arealigned in a line;

FIG. 28 is a flowchart of a processing procedure of a circuit diagramcreation/update;

FIG. 29 is an example of a process selection menu;

FIG. 30 is an example of a display of destination-attribute information;

FIG. 31 is a flowchart of a processing procedure performed on theprocess selection menu; and

FIG. 32 is a functional block diagram of a computer that executes acheck support program.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of the present invention are explained in detailbelow with reference to the accompanying drawings.

An embodiment of the present invention is explained with a printedcircuit board (PCB) 11 shown in FIG. 1 as an example. The printedcircuit board 11 is a back wiring board (BWB) for connecting printedcircuit boards 12 and 13 with each other, and includes connectors CN1and CN2. The connectors CN1 and CN2 each include 10 pins A1 to A10.Among the pins A1 to A10 of the connectors CN1 and CN2, respective setsof pins having the same pin name are connected via signal lines with netnames D1 to D10.

The printed circuit board 12 has a predetermined function, and includesa connector CN1 to be connected to the connector CN1 of the printedcircuit board 11. The connector CN1 includes 10 pins A1 to A5 and B1 toB5.

The pins A1 to A5 are connected to an integrated circuit (IC) 12 a via apart such as a resistor. Signal lines with net names D1 to D5 connectsthe pins A1 to A5 to resistors or the like, respectively, while signallines with net names A-DT1 to A-DT5 connects the resistors or the liketo the IC 12 a, respectively.

Similarly, the pins B1 to B5 are connected to an IC 12 b via a part suchas a resistor. Signal lines with net names D6 to D10 connects the pinsB1 to B5 to resistors or the like, respectively, while signal lines withnet names B-DT1 to B-DT5 connects the resistors or the like to the IC 12b, respectively.

The printed circuit board 13 has a predetermined function, and includesa connector CN2 to be connected to the connector CN2 of the printedcircuit board 11. The connector CN2 includes 10 pins A1 to A5 and B1 toB5.

The pins A1 to A5 are connected to an IC 13 a via a part such as aresistor. Signal lines with net names D1 to D5 connects the pins A1 toA5 to resistors or the like, respectively, while signal lines with netnames A-DT1 to A-DT5 connects the resistors or the like to the IC 13 a,respectively.

Similarly, the pins B1 to B5 are connected to an IC 13 b via a part suchas a resistor. Signal lines with net names D6 to D10 connects the pinsB1 to B5 to resistors or the like, respectively, while signal lines withnet names B-DT1 to B-DT5 connects the resistors or the like to the IC 13b, respectively.

FIG. 2 is a schematic diagram of a design support system according tothe embodiment. The design support system is effective for designing aprinted circuit board to be connected to another printed circuit board.The design support system includes a design-data server 100, apart-information server 200, check support apparatuses 301 to 303, andcomputer aided design (CAD) apparatuses 401 to 403, which are connectedone another via a network 20 such as a local area network (LAN).

The design-data server 100 manages design data such as a designedcircuit diagram and the like, and stores therein association definitiondata created by the check support apparatuses 301 to 303 as a portion ofthe design data. The part-information server 200 manages symbols orspecification information of various parts necessary for editing acircuit diagram.

The check support apparatuses 301 to 303 provide an assistance toeffectively and reliably verify that signals are correctly assigned toconnector pins between printed circuit boards to be connected. The CADapparatuses 401 to 403 are used for electronically designing a printedcircuit board and the like.

The configuration of the design support system shown in FIG. 2 is merelyone example, and can be modified as required. For example, thedesign-data server 100 and the part-information server 200 can beintegrated into one server, or the check support apparatus 301 and theCAD apparatus 401 can be integrated into one apparatus.

The check support apparatuses 301 to 303 are explained below. The checksupport apparatuses 301 to 303 are of like configuration and function inthe same manner, and thus but one of them, the check support apparatus301 is explained in detail.

FIG. 3 is a functional block diagram of the check support apparatus 301.The check support apparatus 301 includes a display unit 310, an inputunit 320, a network interface 330, a control unit 340, and a memory unit350.

The display unit 310 displays various types of information, and includesa liquid crystal display or the like. The input unit 320 is used by auser to provide various types of information, commands and the like.Examples of the input unit 320 include a keyboard, and a mouse. Thenetwork interface 330 is an interface for exchanging information withother devices via the network 20.

The control unit 340 controls the check support apparatus 301. Thecontrol unit 340 includes a design-data acquiring unit 341, aconnector-information display unit 342, a pin-information sorting unit343, an associating unit 344, a checking unit 345, a design-dataupdating unit 346, and a data input/output unit 347.

The design-data acquiring unit 341 acquires design data specified by thedesign-data server 100 or by the CAD apparatuses 401 to 403. Theconnector-information display unit 342 displays, on the display unit310, information on a connector included in the design data acquired bythe design-data acquiring unit 341. The pin-information sorting unit 343sorts information on pins displayed by the connector-information displayunit 342 in a predetermined order. The associating unit 344 defines anassociation of pins to be connected.

Concrete examples of processes performed by the connector-informationdisplay unit 342, the pin-information sorting unit 343, and theassociating unit 344 are explained below. FIG. 4 is an example of acheck screen displayed by the connector-information display unit 342 onthe display unit 310. The check screen as shown in FIG. 4 is displayedafter the check support apparatus 301 reads design data corresponding tothe printed circuit board 11 as a printed circuit board of level 1.

The design-data acquiring unit 341 acquires design data from thedesign-data server 100 in response to an instruction from a user. Thedesign-data acquiring unit 341 exclusively extracts connectorinformation from the design data, and stores the connector informationin a design-data memory 351 of the memory unit 350. Theconnector-information display unit 342 displays the connectorinformation on the check screen. In the example shown in FIG. 4, thecheck screen indicates that the printed circuit board BWB of level 1includes the connectors CN1 and CN2.

In FIG. 4, a box in “Pin” column is simply marked with a symbol “+” toavoid complication due to display of all pieces of information on eachpin. If the user selects a box (“+”) with a mouse or the like, theconnector-information display unit 342 displays a list of information onpins included in a corresponding connector.

Upon receiving an instruction to read design data corresponding to theprinted circuit boards 12 and 13 as printed circuit boards of level 2through the input unit 320, the design-data acquiring unit 341 acquiresthe design data, and exclusively extracts connector information from thedesign data. The connector-information display unit 342 acquires theconnector information, and updates the check screen as shown in FIG. 5.

Referring to FIG. 5, a printed circuit board PCB1 of level 2 includesthe connector CN1, and a printed circuit board PCB2 of level 2 includesthe connector CN2 in addition that the printed circuit board BWB oflevel 1 includes two connectors.

As can be seen in FIG. 5, if the user specifies different levels ofprinted circuit boards to be connected, the connector-informationdisplay unit 342 displays pieces of information on connectors includedin the printed circuit boards on different rows in columns of therespective levels.

In this case, for verifying an assignment of signals to the connectorCN1 of the printed circuit board BWB and to the connector CN1 of theprinted circuit board PCB1, the user selects the connectors CN1 on thecheck screen, and presses “Select” key. Subsequently, theconnector-information display unit 342 displays a list of pininformation of the connectors CN1 on an association screen.

An example of the association screen is shown in FIG. 6. As shown inFIG. 6, a list of net names and pin names of pins included in theselected connectors CN1 is displayed on the association screen. With theassociation screen, the user checks whether signals assigned to the pinsare correct based on the list of pin information for the two connectorsCN1.

Specifically, the user recognizes an association between pinsrespectively included in the two connectors CN1 based on the pin names,and checks whether a signal assigned to an associated pair of the pinsis correct based on the net names of the pins. If a signal is correctlyassigned to the pins, the user selects the associated pair of the pins,and presses “Association” key.

If “Association” key is pressed, the associating unit 344 stores theassociation of the selected pins in an association memory 352 of thememory unit 350. The connector-information display unit 342 adds anasterisk “*” to the top of the name of each selected pin. Pieces ofinformation on the pins are displayed on the same row.

In this manner, an asterisk “*” is added to the top of the name of theassociated pins, and such pins are displayed on the same row. In theexample shown in FIG. 6, a pin A1 of the printed circuit board BWB isassociated with a pin A1 of the printed circuit board PCB1, and a signalis correctly assigned to them. Besides, a pin A2 of the printed circuitboard BWB is associated with a pin A2 of the printed circuit board PCB1,and a signal is correctly assigned to them.

As described above, the association screen is configured to display alist of pin information of connectors to facilitate a user to check theassociation between pins and to check whether signals are correctlyassigned to the pins. Therefore, it is possible to effectively verifythat signals are correctly assigned to pins even when the pin names ofthe associated pins are different from each other. While, in the aboveexample, an asterisk “*” is added to the top of pin names todiscriminate an associated pair of pins, a color of a box or indicationof the pins can be changed instead.

On the other hand, the connector-information display unit 342 displayspin information on the association screen as a default screen in orderas pins have been stored in design data. In the example shown in FIG. 6,the pin information of the printed circuit board BWB and the pininformation of the printed circuit board PCB1 are stored in a properorder, and pieces of information on associated pins are displayed on thesame row. As a result, the user can easily compare the pieces of the pininformation.

However, pin information is not always stored in a preferable orderdepending on design data. Accordingly, the pin-information sorting unit343 sorts pin information in a manner previously specified by the userwhen, for example, the header or the title box of “Pin” column isselected.

The pin-information sorting unit 343 can sort pin information in orderas pins have been stored in design data, or sort pin information byusing a pin name. The pin-information sorting unit 343 can use a wholepin name as a character string, or divide it into a character portionand a numeral portion to sort pin information on a character basis or anumeral basis. Concrete examples other than sorting in stored order areexplained in detail below.

First, it is assumed that a pin name of each pin in the connector CN1 ofthe printed circuit board BWB has a numeral portion embedded with zeroas in a connector 31 shown in FIG. 7, while a pin name of each pin inthe connector CN1 of the printed circuit board PCB1 has a one-digitnumeral portion as in a connector 41 shown in FIG. 7. In this case, asshown in FIG. 8, associated pins are displayed on the same row bysorting pin information using a whole pin name as a character string.

When pin information is sorted by using a whole pin name as a characterstring, pin names are simply sorted by American standard code forinformation interchange (ASCII) code order. This method is effectivewhen the numeral portions of respective pin names have the same numberof digits.

Second, it is assumed that a pin name of each pin in the connector CN1of the printed circuit board BWB has a numeral portion without zeroembedded as in a connector 32 shown in FIG. 9, while a pin name of eachpin in the connector CN1 of the printed circuit board PCB1 is set as inthe connector 41 shown in FIG. 7. In this case, as shown in FIG. 10, ifpin information is sorted by using a whole pin name as a characterstring, associated pins are displayed in different rows.

Thus, pin information is sorted on a character basis by dividing eachpin name into a character portion and a numeral portion, wherebyassociated pins are displayed on the same row as shown in FIG. 11. Inthis method, after the numeral portions of pin names are sorted by anumeric order, the character portions are sorted by ASCII code order.

Third, it is assumed that pin names of pins in the connector CN1 of theprinted circuit board BWB are set as those in a connector 33 shown inFIG. 12, which are set in a different order than those in the connector41. In this case, as shown in FIG. 13, if pin information is sorted on acharacter basis by dividing each pin name into a character portion and anumeral portion, associated pins are displayed in different rows.

Thus, pin information is sorted on a numeral basis by dividing each pinname into a character portion and a numeral portion, whereby associatedpins are displayed on the same row as shown in FIG. 14. In this method,after the character portions of pin names are sorted by ASCII codeorder, the numeral portions are sorted by a numeric order.

The association screen is configured such that the pin-informationsorting unit 343 sorts pin information based on net names when theheader or the title box of “Net” column is selected as shown in FIG. 15.In addition, as shown in FIG. 16, logically-transparent net names can bedisplayed in “Net” column. In such a case, the pin-information sortingunit 343 sorts pin information based on logically-transparent net nameswhen the header or the title box of “Net” column is selected.

As described above, the association screen is configured to sort pininformation of connectors in a predetermined manner, and displayassociated pins on the same row. Therefore, a user can effectively checkwhether signals are correctly assigned to pins.

The method of sorting pin information can be selected by a user, orautomatically selected by the pin-information sorting unit 343 toachieve an optimal result. In this case, the pin-information sortingunit 343 tries all the methods described above, and selects one of themin which the largest number of net names match.

If it is verified that signals assigned to pins are correct and “OK” keyis pressed after the associations of all pins are defined on theassociation screen, associated connectors are displayed on the same rowin the check screen as shown in FIG. 17.

Referring back to FIG. 3, the checking unit 345 checks whether the netnames of associated pair of pins defined by the associating unit 344 arecorrect. The design-data updating unit 346 updates design data and netnames set to the pins to the latest version in advance of a checkperformed by the checking unit 345.

Specifically, when “Check” key is pressed on the check screen, thechecking unit 345 sequentially checks associated pin information. Ifthere is a pair with net names that do not match, the checking unit 345displays detailed pin information of connectors including the pair asshown in FIG. 18, and specifies the pair by a bold-lined frame, adifferent color, or the like.

According to a setting previously specified by a user, the checking unit345 can check associated pin information based on either or both netnames and logically-transparent net names of associated pins. If thereis a pair with logically-transparent net names that do not match, thechecking unit 345 specifies the pair by a bold-lined frame, a differentcolor, or the like.

If a user previously specifies a setting to update design data to thelatest version in advance of a check performed by the checking unit 345,the design-data updating unit 346 acquires the latest design data fromthe design-data server 100 or the CAD apparatuses 401 to 403, andupdates net names stored in association with pin names.

FIG. 19 is a flowchart of a processing procedure of association check.The processing procedure is performed when a setting has been specifiedto update design data to the latest version in advance of a check.

If “Check” key is pressed, the design-data updating unit 346 acquiresthe latest design data (step S101), and updates net names andlogically-transparent net names in association data (step S102). Theterm “association data,” as used herein, refers to data that indicatesassociation or correspondence between pins.

Subsequently, the checking unit 345 acquires an associated pair of pinsfrom the association data (step S103). If all pairs of pins have alreadybeen acquired from the association data (YES at step S104), the processends.

On the other hand, if there is a pair of pins yet to be acquired, thepair is acquired from the association data (NO at step S104), and thenet names of the pins are compared. If the net names of the pins match(YES at step S105), the process control returns to step S103 to acquirea next pair of pins. If the net names of the pins do not match (NO atstep S105), an error indicating a mismatch between the net names isdisplayed (step S106), and the process control returns to step S103 toacquire a next pair of pins.

In this manner, by checking a match and a mismatch between net names allat once, it is possible to verify that net names are correctly set to aprinted circuit board to be connected and to improve a quality of designdata. Furthermore, by updating net names to the latest version inadvance of a check, it is possible to detect that a net name has beenincorrectly updated or to check whether the net name incorrectly updatedhas been corrected.

Although, in the above explanation, a pair of pins with net names orlogically-transparent net names that do not match is highlighted on thecheck screen, a list of such pairs can be output as an electric file ora document.

If the check support apparatus 301 and the CAD apparatus 401 areintegrally configured, a circuit diagram of a portion corresponding tomismatched pins, i.e., pins with net names or logically-transparent netnames that do not match, can be displayed to assist a user to check it.A screen for editing the circuit diagram of the portion corresponding tothe mismatched pins can also be automatically displayed to assist theuser to correct the net names or the logically-transparent net names.

The data input/output unit 347 exchanges the association data, i.e.,data indicating the association of pins, with other devices via thenetwork 20. The data input/output unit 347 outputs the association datain an electric file as an association file.

FIG. 20 is an example of the association file. In FIG. 20, a comment rowstarts with a number sign “#”. A block start with “@UNIT” containsinformation on a drawing and a printed circuit board described in thedrawing.

A block start with “@CONNECT” contains information on associated pairsof pins. A block start with “@UNCONNECT” contains information on pinsyet to be associated. In the block start with “@CONNECT”, information ona pin at a high level specified upon reading of design data is stored asa parent, while information on a pin at a low level is stored as achild.

The association file shown in FIG. 20 stores only associations betweenthe connector CN1 of the printed circuit board BWB and the connector CN1of the printed circuit board PCB1. However, when an association betweenthe connector CN2 of the printed circuit board BWB and the connector CN2of the printed circuit board PCB2 is once defined, the association ofpins of the connectors CN2 is also stored in the association file.Accordingly, by referring to the association file, it is possible tocheck associations and connections, via the printed circuit board BWB,between pins of the connector CN1 of the printed circuit board PCB1 andpins of the connector CN2 of the printed circuit board PCB2.

Referring back to FIG. 3, the memory unit 350 stores therein varioustypes of information, and includes the design-data memory 351 and theassociation memory 352. The design-data memory 351 stores thereinconnector information extracted from data acquired by the design-dataacquiring unit 341. The association memory 352 stores thereininformation on the association of pins defined by the associating unit344.

FIG. 21 is an example of the structure of design data. As shown in FIG.21, design data stored in the design-data memory 351 contains designinformation 351 a that indicates a drawing and a printed circuit boardincluding a connector, connector information 351 b that contains libraryaccess key and the like for acquiring a part name of the connector orinformation on the connector from the part-information server 200, andpin information 351 c that contains information on pins included in theconnector.

FIG. 22 is an example of the structure of association data. As shown inFIG. 22, association data stored in the association memory 352 containsconnector association information 352 a that indicates an associationbetween connectors, and pin association information 352 b that indicatesan association between pins.

The CAD apparatuses 401 to 403 shown in FIG. 2 are explained below. TheCAD apparatuses 401 to 403 are of like configuration and function in thesame manner, and thus but one of them, the CAD apparatus 401 isexplained in detail.

FIG. 23 is a functional block diagram of the CAD apparatus 401. The CADapparatus 401 includes a display unit 410, an input unit 420, a networkinterface 430, a control unit 440, and a memory unit 450.

The display unit 410 displays various types of information, and includesa liquid crystal display or the like. The input unit 420 is used by auser to provide various types of information, commands or the like.Examples of the input unit 420 include a keyboard, and a mouse. Thenetwork interface 430 is an interface for exchanging information withother devices via the network 20.

The control unit 440 controls the CAD apparatus 401. The control unit440 includes an editing unit 441, an association-data acquiring unit442, a part-information acquiring unit 443, a layout-condition acquiringunit 444, a circuit diagram creating/updating unit 445, an attributedisplay unit 446, and a circuit display unit 447.

The editing unit 441 edits a drawing, and is equivalent to that includedin a general CAD apparatus. The association-data acquiring unit 442acquires association data created by the check support apparatuses 301to 303. The part-information acquiring unit 443 acquires a symbol or thelike that indicates a part from the part-information server 200.

The layout-condition acquiring unit 444 acquires a layout condition orrules for creating a circuit diagram of a printed circuit board based onthe association data. The circuit diagram creating/updating unit 445creates and updates the circuit diagram of the printed circuit boardbased on the association data. The attribute display unit 446 displaysattribute information of pins to be associated on an editing screen. Thecircuit display unit 447 displays an editing screen of the pin to beassociated.

With the association-data acquiring unit 442, the part-informationacquiring unit 443, the layout-condition acquiring unit 444, and thecircuit diagram creating/updating unit 445, a circuit diagram of aprinted circuit board can be created or updated based on associationdata.

An example of a circuit diagram created based on association data isshown in FIG. 24. In the circuit diagram shown in FIG. 24 is arranged asymbol 51 corresponding to a connector including pins whose associationis defined. Part names are added to the pins, and signal lines with netnames are extended from the pins, respectively. At the end of eachsignal line is a signal connector 52.

When it is required to create or update a circuit diagram of a printedcircuit board based on association data, the layout-condition acquiringunit 444 displays a circuit-diagram creation/update screen on thedisplay unit 410 through which a user can input necessary information.

FIG. 25 is an example of the circuit-diagram creation/update screen. Asshown in FIG. 25, the circuit-diagram creation/update screen contains anarea for specifying an association file, an area for specifying a shapeand a position of a target part, an area for specifying an order ofoutputting parts, and an area for specifying a layout condition of theparts. Based on the layout condition, symbols of the parts (connectors)are laid out on a circuit diagram.

If “Arrange sequentially” is specified as the layout condition of parts,symbols of connectors are sequentially arranged as shown in FIG. 26. Onthe other hand, if “Align identical parts” is specified as the layoutcondition, symbols corresponding to an identical connector are alignedin the same line.

When a connector includes a number of pins, the connector may be dividedinto a plurality of portions such that the portions can be indicated bydifferent symbols. All the symbols of the connector are registered inthe part-information server 200. For example, three symbols CN1-1 toCN1-3 shown in FIGS. 26 and 27 correspond to one connector. If a circuitdiagram contains a plurality of symbols for a single connector, it isoften difficult to discriminate which symbol corresponds to whichconnector. However, by arranging symbols corresponding to an identicalconnector in the same line, the symbols can easily be discriminated.

A processing procedure performed after required information is input onthe circuit-diagram creation/update screen is shown in FIG. 28. Theassociation-data acquiring unit 442 acquires and reads an associationfile specified on the circuit-diagram creation/update screen (stepS201). The circuit diagram creating/updating unit 445 selects a parentconnector from the association file (step S202).

If all parent connectors have already been selected (YES at step S203),the circuit diagram creating/updating unit 445 ends the process. Ifthere is a parent connector yet to be selected (NO at step S203), theparent connector is selected. When the parent connector is not arrangedon the circuit diagram (NO at step S204), the circuit diagramcreating/updating unit 445 instructs the part-information acquiring unit443 to acquire the symbol from the part-information server 200 using alibrary access key (step S205).

The symbol acquired is arranged on a predetermined position on thecircuit diagram according to a specified condition (step S206). Afteradding a signal line to the symbol (step S207), the part name and thenet name are added to the symbol and the signal line, respectively (stepS208). On the other hand, if the selected parent connector has alreadybeen arranged on the circuit diagram (YES at step S204), the net name isupdated so that the net names on the circuit diagram correspond to thosein the association file (step S209).

After the above process for a selected connector, the circuit diagramcreating/updating unit 445 selects a next connector (step S202).Although creation of a circuit diagram is explained with parentconnectors in an association file, a circuit diagram can be created forchild connectors in a similar manner.

Referring back to FIG. 23, if a pin of a connector is selected whiledesign data is being edited and a predetermined operation is performed,the attribute display unit 446 displays information on a correspondingpin (destination pin) of a printed circuit board (destination printedcircuit board) to be connected to the pin on the display unit 410. Thecircuit display unit 447 displays design data of a portion correspondingthe destination pin of the destination printed circuit board on thedisplay unit 410.

For example, if a mouse is right-clicked in such a state that a pin A3is selected while design data of the printed circuit board 12 is beingedited, the CAD apparatus 401 displays a process selection menu 61 asshown in FIG. 29.

If “Destination-attribute display” is selected in the process selectionmenu 61, the attribute display unit 446 displays a popup window 62showing information on the pin A3 of the connector CN1 of the printedcircuit board 11 as shown in FIG. 30. The information shown in the popupwindow 62 includes at least the pin name and the net name of the pin A3.Preferably, the pin name and the net name are acquired from the designdata including the printed circuit board 11.

In this manner, with a display of information on destination pins of adestination printed circuit boards, a user can carry out editing workwhile checking whether signals are correctly assigned to the pins.

If “Destination-circuit display” is selected in the process selectionmenu 61, the circuit display unit 447 opens an editing screen of thecircuit diagram of the printed circuit board 11 to be connected, andzooms in a portion corresponding to the pin A3 of the connector CN1 onthe display.

If “Destination-circuit display (BWB transparent)” is selected in theprocess selection menu 61, the circuit display unit 447 opens an editingscreen of the circuit diagram of the printed circuit board 13 to beconnected via the printed circuit board 11 that is a BWB, and zooms in aportion corresponding to the pin A3 of the connector CN2 on the display.

In this manner, by displaying an editing screen of a portioncorresponding to a destination pin of a destination printed circuitboard or a destination printed circuit board to be connected via a BWB,a user can easily change an assignment of a signal to the pin.

FIG. 31 is a flowchart of a processing procedure performed on theprocess selection menu 61. As shown in FIG. 31, after the processselection menu 61 is displayed (step S301), if “Destination-attributedisplay” is selected (YES at step S302), the attribute display unit 446acquires information on a destination pin of a destination printedcircuit board (step S303), and displays the information (step S304).

If “Destination-circuit display” is selected in the process selectionmenu 61 (NO at step S302, YES at step S305), the circuit display unit447 acquires information on a destination printed circuit board (stepS306). If “Destination-circuit display (BWB transparent)” is selected(NO at step S302, NO at step S305), the circuit display unit 447acquires information on a destination printed circuit board to beconnected via a BWB (step S307).

In this manner, after acquiring the information on the printed circuitboard, when the editing screen of the circuit diagram of the printedcircuit board is not displayed (NO at step S308), the circuit displayunit 447 displays the editing screen of the circuit diagram (step S309).Thereafter, on the editing screen displayed, the circuit display unit447 zooms in a portion corresponding to the destination pin associatedwith a pin selected (step S310).

Attribute information of a destination printed circuit board is requiredto be read in advance by the association-data acquiring unit 442 andstored in an association memory 452 of the memory unit 450 such that theattribute display unit 446 and the circuit display unit 447 can realizethe above functions. The association-data acquiring unit 442 canautomatically read the attribute information upon start of editing work,or read the attribute information in response to an instruction from auser.

Referring back to FIG. 23, the memory unit 450 stores therein varioustypes of information, and includes a design-data memory 451 and theassociation memory 452. The design-data memory 451 stores therein designdata of a printed circuit board to be edited. The association memory 452stores therein information indicating the association of pins defined bythe check support apparatuses 301 to 303.

As described above, the check support apparatuses 301 to 303 and the CADapparatuses 401 to 403 according to the embodiment include variousfunctions for effectively designing a printed circuit board to beconnected to another printed circuit board.

The check support apparatus and the CAD apparatus are explained above ashardware; however, they can be implemented as software. For example, acomputer program that realizes the same function as the control unit 340of the check support apparatus 301 can be executed on a computer toimplement the check support apparatus 301. Similarly, a computer programthat realizes the same function as the control unit 440 of the CADapparatus 401 can be executed on a computer to implement the CADapparatus 401.

The check support apparatus and the CAD apparatus can also beimplemented as single software. Specifically, a computer program thatrealizes the same functions as both the control unit 340 and the controlunit 440 can be executed on a computer to implement both the checksupport apparatus 301 and the CAD apparatus 401.

Such a computer is explained that executes a computer program(hereinafter, “check support program”) to implement the functions of thecontrol unit 340. A computer program that implements the functions ofthe control unit 440 is executed by a computer having a similarconfiguration.

FIG. 32 is a functional block diagram of a computer 1000 that executes acheck support program 1071. The computer 1000 includes a centralprocessing unit (CPU) 1010, an input device 1020, a display device 1030,a medium reader 1040, a network interface 1050, a random access memory(RAM) 1060, and a hard disk drive (HDD) 1070, which are connected oneanother via a bus 1080.

The CPU 1010 executes various operation processes. The input device 1020receives input of data from a user. The display device 1030 displaysvarious types of information thereon. The medium reader 1040 reads aprogram and the like from a recording medium. The network interface 1050exchanges data with another computer via a network. The RAM 1060temporarily stores therein various types of information.

The HDD 1070 stores therein the check support program 1071 having thesame function as the control unit 340, and check support data 1072corresponding to various data stored in the memory unit 350. The checksupport data 1072 can be distributed as appropriate and stored inanother computer connected via the network.

The CPU 1010 loads the check support program 1071 from the HDD 1070 intothe RAM 1060, and executes the check support program 1071 to perform acheck support process 1061. In the check support process 1061, the checksupport data 1072 is loaded as appropriate into an area allocated forthe check support process 1061 on the RAM 1060, and various dataprocesses are performed based on the check support data 1072.

The check support program 1071 need not necessarily stored in the HDD1070. The check support program 1071 can be stored in a recording mediumsuch as a compact disc-read only memory (CD-ROM), and read and executedby the computer 1000. The check support program 1071 can also be storedin another computer (or a server) connected to the computer 1000 via apublic line, the Internet, a local area network (LAN), a wide areanetwork (WAN), or the like, and downloaded therefrom to be executed.

As set forth hereinabove, according to an embodiment of the presentinvention, it is possible to effectively design a printed circuit boardto be connected to another printed circuit board via connectors.

Although the invention has been described with respect to a specificembodiment for a complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art that fairly fall within the basic teaching herein setforth.

1. A computer aided design (CAD) apparatus for designing a circuitdiagram, comprising: an association-data acquiring unit that acquiresassociation data that defines an association between a pin of a firstconnector and a pin of a second connector to be connected to the firstconnector, and an assignment of a signal to the pins; a part-informationacquiring unit that acquires information including a symbol of the firstconnector; a layout-condition acquiring unit that acquires a layoutcondition to lay out the symbol on a circuit diagram; and a circuitdiagram editing unit that lays out, when the symbol has not yet beenlaid out on the circuit diagram, the symbol on the circuit diagram basedon the layout condition, and adds a net name indicating the signalassigned to the pins to the symbol.
 2. The CAD apparatus according toclaim 1, wherein, when the symbol has already been laid out on thecircuit diagram, the circuit diagram editing unit updates an old netname added to the symbol.
 3. The CAD apparatus according to claim 1,wherein, when the symbol of the first connector includes a plurality ofsymbols, the circuit diagram editing unit lays out the symbols such thatthe symbols are distinguishable from other symbols.
 4. A non-transitorycomputer-readable recording medium that stores therein a computerprogram for designing a circuit diagram that causes a computer toexecute: acquiring association data that defines an association betweena pin of a first connector and a pin of a second connector to beconnected to the first connector, and an assignment of a signal to thepins; acquiring information including a symbol of the first connector;acquiring a layout condition to lay out the symbol on the circuitdiagram; and laying out, when the symbol has not yet been laid out onthe circuit diagram, the symbol on the circuit diagram based on thelayout condition, and adding a net name indicating the signal assignedto the pins to the symbol.
 5. The non-transitory computer-readablerecording medium according to claim 4, further comprising updating, whenthe symbol has already been laid out on the circuit diagram, an old netname added to the symbol.
 6. The non-transitory computer-readablerecording medium according to claim 4, wherein the laying out includeslaying out, when the symbol of the first connector includes a pluralityof symbols, the symbols such that the symbols are distinguishable fromother symbols.
 7. A method of designing a circuit diagram, comprising:acquiring association data that defines an association between a pin ofa first connector and a pin of a second connector to be connected to thefirst connector, and an assignment of a signal to the pins; acquiringinformation including a symbol of the first connector; acquiring alayout condition to lay out the symbol on the circuit diagram; andlaying out, using a processor, when the symbol has not yet been laid outon the circuit diagram, the symbol on the circuit diagram based on thelayout condition, and adding a net name indicating the signal assignedto the pins to the symbol.
 8. The method according to claim 7, furthercomprising updating, when the symbol has already been laid out on thecircuit diagram, an old net name added to the symbol.
 9. The methodaccording to claim 7, wherein the laying out includes laying out, whenthe symbol of the first connector includes a plurality of symbols, thesymbols such that the symbols are distinguishable from other symbols.